全文获取类型
收费全文 | 311283篇 |
免费 | 4230篇 |
国内免费 | 1935篇 |
专业分类
化学 | 144113篇 |
晶体学 | 4833篇 |
力学 | 16657篇 |
综合类 | 72篇 |
数学 | 47475篇 |
物理学 | 104298篇 |
出版年
2021年 | 2212篇 |
2020年 | 2463篇 |
2019年 | 2572篇 |
2018年 | 11386篇 |
2017年 | 12106篇 |
2016年 | 8253篇 |
2015年 | 3826篇 |
2014年 | 4473篇 |
2013年 | 10274篇 |
2012年 | 12555篇 |
2011年 | 21717篇 |
2010年 | 13714篇 |
2009年 | 13681篇 |
2008年 | 18963篇 |
2007年 | 22356篇 |
2006年 | 8626篇 |
2005年 | 14121篇 |
2004年 | 10168篇 |
2003年 | 9327篇 |
2002年 | 7244篇 |
2001年 | 6872篇 |
2000年 | 5505篇 |
1999年 | 4113篇 |
1998年 | 3275篇 |
1997年 | 3213篇 |
1996年 | 3152篇 |
1995年 | 2869篇 |
1994年 | 2685篇 |
1993年 | 2528篇 |
1992年 | 2854篇 |
1991年 | 2822篇 |
1990年 | 2754篇 |
1989年 | 2538篇 |
1988年 | 2596篇 |
1987年 | 2578篇 |
1986年 | 2394篇 |
1985年 | 3091篇 |
1984年 | 3350篇 |
1983年 | 2734篇 |
1982年 | 2899篇 |
1981年 | 2879篇 |
1980年 | 2725篇 |
1979年 | 2824篇 |
1978年 | 2928篇 |
1977年 | 2848篇 |
1976年 | 2959篇 |
1975年 | 2726篇 |
1974年 | 2689篇 |
1973年 | 2854篇 |
1972年 | 1796篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
Quantitative analysis of polyhexamethylene guanidine (PHMG) oligomers via matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry with an ionic‐liquid matrix
下载免费PDF全文
![点击此处可从《Rapid communications in mass spectrometry : RCM》网站下载免费的PDF全文](/ch/ext_images/free.gif)
104.
105.
Tereshchenko E. D. Cherniakov S. M. Yurik R. Yu. Rietveld M. T. Häggström I. 《Radiophysics and Quantum Electronics》2020,62(10):667-676
Radiophysics and Quantum Electronics - We present the results of comparing the total electron content measurements based on GLONASS satellite signals and the EISCAT UHF incoherent scatter radar... 相似文献
106.
107.
Development of an LC‐MS/MS method for determining the pharmacokinetics of clonidine following oral administration of Zhenju antihypertensive compound
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jing Qin Limin Wang Lihong Wu Jun Chen Teng Shen Yongji Li Limei Han Jianxin Wang 《Biomedical chromatography : BMC》2015,29(7):1068-1075
Zhenju antihypertensive compound (ZJAHC) is a combined Chinese–Western medicine formula including clonidine (CLO), hydrochlorothiazide (HCT), rutin, Chrysanthemum indicum extract and pearl powder. Compared with CLO preparations, ZJAHC shows improved activities and decreased adverse effects. It is believed that the side effects of CLO are caused by its high peak plasma concentration. Hence, study of the influence of ZJAHC on the pharmacokinetic behaviors of clonidine seems essential. In present study, the plasma concentrations of CLO were determined with a liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method. The MS/MS transitions monitored for clonidine and internal standard were 230.2 → 213.1 and 152.2 → 110.2, respectively. The analyte was quantified in a single run within 3 min. The pharmacokinetic study showed that the area under the plasma concentration–time curve of CLO in ZJAHC (60 µg/kg CLO) was similar to that of CLO‐HCT‐high (120 µg/kg CLO) but the peak concentration was much lower than that in CLO‐HCT‐high. ZJAHC could enhance the bioavailability without greatly increasing peak concentration of clonidine. This comprehensive effect of enhancing the bioavailability and avoiding the high peak plasma concentration for CLO might mainly result from the co‐contribution of Western medicine and traditional Chinese medicine (TCM), while the effect of TCM was stronger than that of Western medicine. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
108.
Facile non‐lithographic route to highly aligned silica nanopatterns using unidirectionally aligned polystyrene‐block‐polydimethylsiloxane films
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhe Qiang Maurice L. Wadley Bryan D. Vogt Kevin A. Cavicchi 《Journal of Polymer Science.Polymer Physics》2015,53(15):1058-1064
Thin films (monolayer and bilayer) of cylinder forming polystyrene‐block‐polydimethylsiloxane (PS‐b‐PDMS) were shear aligned by the swelling and deswelling of a crosslinked PDMS pad that was physically adhered to the film during solvent vapor annealing. The nanostructures formed by self‐assembly were exposed to ultraviolet‐ozone to partially oxidize the PDMS, followed by calcination in air at 500 °C. In this process, the PS segments were fully decomposed, while the PDMS yielded silica nanostructures. The highly aligned PDMS cylinders were thus deposited as silica nanolines on the silicon substrate. Using a bilayer film, the center‐to‐center distance of these features were effectively halved from 38 to 19 nm. Similarly, by sequential shear‐alignment of two distinct layers, a rhombic array of silica nanolines was fabricated. This methodology provides a facile route to fabricating complex topographically patterned nanostructures. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1058–1064 相似文献
109.
110.
Dr. Si-Yong Qin Yan Jiang Dr. Han Sun Han Liu Prof. Ai-Qing Zhang Prof. Xinxiang Lei 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17245-17251
Residual dipolar coupling (RDC), a robust anisotropic NMR parameter for structural elucidation of organic molecules, is only accessible in an anisotropic environment. Herein, we introduce a novel alignment medium based on the molecular self-assembly of oligopeptide amphiphile (OPA). This medium is compatible with different intermediate and polar solvent systems, such as CD3OD, [D6]DMSO, and D2O. The preparation of the OPA-based medium is simple and rapid, while only very weak background signals were observed from OPAs. Furthermore, we show that the purity of OPA has only a minor influence on the quality of the RDC data. These advantages allow RDC measurements of organic molecules with different polarities and solubilities with high efficiency and accuracy. 相似文献